1. Field of the Invention
The present invention relates to a dishwashing machine, and more particularly to an electric control apparatus for controlling the washing or rinsing operation of the dishwashing machine in accordance with the tableware to be cleaned.
2. Description of the Prior Art
There has been proposed a dishwashing machine of the domestic type in which wash water of constant temperature (for instance 60.degree. C.) in a wash tank is sprayed into a washing chamber to wash tableware placed in the washing chamber. When the sprayed wash water is drained outward through the wash tank, wash water of 60.degree. C. newly supplied into the wash tank from a source of hot water is sprayed into the washing chamber to rinse the washed tableware and is returned into the wash tank to be utilized for wash other tableware. In such a dishwashing machine of the commercial type, wash water of constant temperature (for instance 65.degree. C.) is sprayed into a washing chamber to wash tableware placed in the washing chamber. Then, fresh water of high temperature (for instance 85.degree. C.) from a source of hot water is sprayed directly into the washing chamber to rinse the washed tableware. When fresh water flows down into the wash tank, the surplus wash water in the wash tank is drained outward through an overflow pipe arranged in the wash tank, and wash water still remaining in the wash tank is utilized for in place therefor other tableware.
In the dishwashing machines as described above, it should be however recognized that even if the tableware is earthenware, plastic ware or glassware, the temperature of water in washing or rinsing the tableware is maintained in the above-mentioned constant value to cause the following disadvantages.
Firstly, in case temperature of water in rinsing the glassware is high, the speed for drying the rinsed glassware is maintained at a high value. Thus, such composition as magnesium, calcium and iron included within the water for rinsing the glassware coagulates on a surface of the glassware, causing bad finish in rinsing the glassware. Furthermore, when the glassware is repetitively rinsed by water of high temperature, composition on the surface of the glassware is gradually changed to make dull the surface of the glassware.
Secondly, it is noted that high temperature of water in washing or rinsing chilled glassware causes remarkable temperature difference to a surface of the chilled glassware. This results in breakage of the glassware during washing. It is further noted that when ice is put into the glassware warmed during washing and rinsing as described above, the warmed glassware is suddenly cooled causing breakage of the warmed glassware.
Thirdly, in such dishwashing machines as described above, it is to be noted that temperature of water in washing or rinsing is determined in a high value on a basis of earthenware of large heat capacity such as dishes, bowls or the like. Thus, glassware of small heat capacity is remarkably warmed in washing and rinsing, causing occupational diseases such as sodden fingers, burned fingers or the like. In addition, waiting for the cooling of the warmed glassware increases time in being unable to use the glassware. This results in the need for increasing spare glassware.
Fourthly, it is noted that high temperature of water in washing or rinsing plastic ware causes vanishing of gloss or picture on a surface of the plastic ware. This shortens durable time of the plastic ware and exaggerates the difference between new and old plastic ware.